1. Field of the Invention
This invention relates to a type carrier for use in impact-type printing machines and more in particular to an improved type carrier having a plurality of types which may be selectively impacted by either a flat hammer or detentable hammer to produce an imprint of the virtually equal quality when used in an impact-type printing machine such as typewriters, line-printers and wordprocessors.
2. Background of the Invention
A type carrier which has a plurality of types and which is subjected to rotation with or without translation to bring the desired type into the printing position is well known. In such a type carrier, a plurality of types are usually arranged in a circle. Thus, when mounted in a printing machine, the type carrier is rotated to locate the desired type at the printing position and then the thus positioned type is impacted by a hammer to print a character on print paper. If a plurality of types are arranged in two or more circles, the type carrier is also subjected to a translational motion in positioning the desired type.
One prior art type carrier is illustratively shown in FIG. 1. The type carrier 1 shown in FIG. 1 is a disc-shaped type carrier, which is often referred to as a printing wheel and which includes a hub 2 provided with a center hole 2a through which a rotary shaft (not shown) is to be inserted. The printing wheel 1 also includes a plurality of fingers 3 which extend radially straight from the hub 2. Each of the fingers 3 is provided with a character pad 4, or printing section, at its tip end. A type is provided on the front surface of the printing section 4, the back surface of which presents as an impacting surface onto which a printing hammer (not shown) is to be impacted for forming an imprint.
Another prior art type carrier 1' is shown as mounted in printing arrangement in FIG. 2. The type carrier 1' is a cap-shaped type carrier which includes a hub 2 provided with a center hole 2a into which a rotary shaft 15 is fitted. The type carrier 1' also includes a plurality of fingers 3 which extend radially from the hub 2. As shown, the fingers 3 are at a certain angle with respect to the rotating axis of the shaft 15. At the end of each of the fingers 3 is provided with a printing section 4, or character pad, which is again angled against the corresponding finger 3. It should be noted, therefore, that the front and back surfaces of the printing sections 4 are generally in parallel with the rotating axis of the shaft 15 as different from the type carrier 1 of FIG. 1, in which the front and back surfaces of the printing sections 4 are generally perpendicular to the rotating axis. The finger 3 may serve as a connection between the printing section 4 and the hub 2.
In the example shown in FIG. 2, the type carrier 1' includes a pair of types 16a and 16b provided on the front surface of each of the printing sections 4 spaced apart from each other. Thus, the types 16a form a first circle of type arrangement; whereas, the types 16b form a second circle of type arrangement. Disposed inside the type carrier 1' is an impact device 18 which includes a reciprocatingly movable hammer 15. On the other hand, printpaper 19 is passed around a platen 20, and an ink ribbon 21 is disposed between the type carrier 1' and the platen 20, passing through the printing section.
In operation, the type carrier 1' is rotated with or without translational movement along the rotating axis to locate the desired type at the printing position. Then, the hammer 15 is advanced to press the desired type against the print paper 19 with the ink ribbon 21 inbetween, thereby forming an imprint of the desired type on the print paper 19. It should thus be understood that the fingers 3 possess a certain degree of elastisity.
FIG. 3 shows another conventional disc-shaped type carrier 1" which includes a single type 16a or 16b on the front surface of each of the printing sections. A pair of type carriers 1", 1" is fixedly mounted on a common rotary shaft 23. The operation of this arrangement is similar to that of FIG. 2 except the impacting process. That is, in the arrangement of FIG. 3, after locating the desired type at the printing position, the shaft 23 is inclined in the direction indicated by the arrow A so that a flange 24 is brought into engagement with a stopper 25, which, in turn, will cause a hammer 15 to press the desired type against the platen 20, thereby forming an imprint on the print paper 19.
FIGS. 4(A) and (B) show several structures of the printing section, particularly its back surface, of the fingers used in prior art type carriers as shown in FIGS. 1 through 3. FIG. 4(A) shows a non-detentable structure; whereas, FIG. 4(B) shows a detentable structure.
FIG. 4(A) shows a non-detentable combination which includes the printing section 4a having a flat back surface 26a and the hammer 15a having a flat impact surface 27a. The printing section 4a includes a type 16 on its front surface. Thus, when the hammer 15a is advanced in the direction indicated by the arrow B, the impact surface 27a comes into contact with the flat back surface of the printing section 4a, thereby deflecting the supporting finger 3 to press the type 16 against the platen (not shown). With such a combination, the impacting force may be uniformly applied to the type; however, there is a chance of causing misalignment or smearing of the printed character if the hammer 15a presses the printing section 4a while it is still in vibration, such as in high-speed printing operation.
FIG. 4(B) shows a detentable combination which includes the printing section 4b having a triangular prism member 26b and the hammer 15b having a recessed impacting surface 27b in the shaped of "V." The V-shaped recess 27b' has two sloped surfaces which are engageable with the two sloped side surfaces of the prism member 26b, which is provided to project from the back surface 26a of the printing section 4b. In this case, when the hammer 15b is moved toward the printing section 4b as indicated by the arrow B to bring the V-shaped recess 27b' into engagement with the prism member 26b, the printing section 4b is forcibly brought into the aligned position so that the probability of misalignment may be precluded. However, such a structure requires the use of a specially shaped hammer and it is disadvantageous since limitations are imposed upon the variety in using replaceable type carriers.